<?php
//isset你用对了吗
$map = array(
    'name'=>'小丽',
    'age'=>18,
    'other'=>null
);
foreach ($map as $key=>$val){
    echo $key.'值：'.print_r($val,true).PHP_EOL;
    if(array_key_exists($key,$map)){
        echo $key."存在".PHP_EOL;
    }else{
        echo $key."不存在".PHP_EOL;
    }
    echo "------".PHP_EOL;
}